Polymer interlayers having improved optical properties

ABSTRACT

An interlayer comprised of a thermoplastic resin, at least one high refractive index plasticizer and, optionally, a conventional plasticizer. The use of a thermoplastic resin, a high refractive index plasticizer, and, optionally, a conventional plasticizer reduces or minimizes the optical defects caused by different refractive indices without sacrificing other characteristics of the interlayer.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.14/299,996, filed Jun. 9, 2014, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/833,205, filed Jun. 10, 2013,the entire disclosure of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure is related to the field of polymer interlayers formultiple layer panels and multiple layer panels having at least onepolymer interlayer sheet. Specifically, this disclosure is related tothe field of polymer interlayers having improved optical properties, andmore specifically, to polymer interlayers comprising a high refractiveindex plasticizer.

2. Description of Related Art

Multiple layer panels are generally panels comprised of two sheets of asubstrate (such as, but not limited to, glass, polyester, polyacrylate,or polycarbonate) with one or more polymer interlayers sandwichedtherebetween. The laminated multiple layer glass panels are commonlyutilized in architectural window applications, in the windows of motorvehicles and airplanes, and in photovoltaic solar panels. The first twoapplications are commonly referred to as laminated safety glass. Themain function of the interlayer in the laminated safety glass is toabsorb energy resulting from impact or force applied to the glass, tokeep the layers of glass bonded even when the force is applied and theglass is broken, and to prevent the glass from breaking up into sharppieces. Additionally, the interlayer may also give the glass a muchhigher sound insulation rating, reduce UV and/or IR light transmission,and enhance the aesthetic appeal of the associated window. In regard tothe photovoltaic applications, the main function of the interlayer is toencapsulate the photovoltaic solar panels which are used to generate andsupply electricity in commercial and residential applications.

The interlayer may be a single layer, a combination of more than onesingle layer, a multilayer that has been coextruded, a combination of atleast one single layer and at least one multilayer, or a combination ofmultilayer sheets.

In order to achieve the certain property and performance characteristicsfor the glass panel, it has become common practice to utilize multiplelayer or multilayered interlayers. As used herein, the terms“multilayer” and “multiple layers” mean an interlayer having more thanone layer, and multilayer and multiple layer may be usedinterchangeably. Multiple layer interlayers typically contain at leastone soft layer and at least one stiff layer. Interlayers with one soft“core” layer sandwiched between two more rigid or stiff “skin” layershave been designed with sound insulation property for the glass panel.Interlayers having the reverse configuration, that is, with one stifflayer sandwiched between two more soft layers have been found to improvethe impact performance of the glass panel. Examples of multiple layerinterlayers also include the interlayers with at least one “clear” ornon-colored layer and at least one colored layer. Other examples ofmultiple layer interlayers include interlayers with at least two layerswith different colors. The colored layer typically contains pigments ordyes or some combination of pigments and dyes. The layers of theinterlayer are generally produced by mixing a polymer resin such aspoly(vinyl butyral) with one or more plasticizers and melt processingthe mix into a sheet by any applicable process or method known to one ofskill in the art, including, but not limited to, extrusion, with thelayers being combined by processes such as co-extrusion and lamination.Other additional ingredients may optionally be added for various otherpurposes. After the interlayer sheet is formed, it is typicallycollected and rolled for transportation and storage and for later use inthe multiple layer glass panel, as discussed below.

Contemplated polymer interlayers include, but are not limited to,polyvinyl acetals (PVA) (such as polyvinyl butyral (PVB)), polyurethane(PU), poly(ethylene-co-vinyl acetate) (EVA), polyvinylchloride (PVC),polyethylenes, polyolefins, ethylene acrylate ester copolymers,poly(ethylene-co-butyl acrylate), silicone elastomers, epoxy resins, andacid copolymers such as ethylene/carboxylic acid copolymers and itsionomers, derived from any of the foregoing possible thermoplasticresins. Multilayer laminates can include multiple layer glass panels andmultilayer polymer films. In certain embodiments, the multiple polymerfilms in the multilayer laminates may be laminated together to provide amultilayer film or interlayer. In certain embodiments, these polymerfilms may have coatings, such as metal, silicone or other applicablecoatings known to those of ordinary skill in the art. The individualpolymer films which comprise the multilayer polymer films may belaminated together using an adhesive as known to those of ordinary skillin the art. The following offers a simplified description of the mannerin which multiple layer glass panels are generally produced incombination with the interlayers. First, at least one polymer interlayersheet (single or multilayer) is placed between two substrates and anyexcess interlayer is trimmed from the edges, creating an assembly. It isnot uncommon for multiple polymer interlayer sheets or a polymerinterlayer sheet with multiple layers (or a combination of both) to beplaced within the two substrates creating a multiple layer glass panelwith multiple polymer interlayers. Then, air is removed from theassembly by an applicable process or method known to one of skill in theart; e.g., through nip rollers, vacuum bag or another deairingmechanism. Additionally, the interlayer is partially press-bonded to thesubstrates by any method known to one of ordinary skill in the art. In alast step, in order to form a final unitary structure, this preliminarybonding is rendered more permanent by a high temperature and pressurelamination process, or any other method known to one of ordinary skillin the art such as, but not limited to, autoclaving.

One of the problems in the manufacture of multilayer laminate glasspanels having multiple layer interlayers is the presence of mottle inthe final unitary structure. The term “mottle” refers to anobjectionable visual defect in the final unitary structure, namely theappearance of uneven spots, a form of optical distortion. Stateddifferently, mottle is a measure of the graininess or texture formedfrom the optical effect of reflecting non-uniform distorted interfacesof the inner polymer interlayer or polymer interlayers.

In multiple layer interlayers having at least one soft layer and atleast one stiff layer, the mottle is caused by small scale surfacevariations at the interfaces between the layers wherein the individuallayers (or the soft and stiff layers) have different refractive indices.When the polymer interlayer is produced, surface roughness is formed atthe utmost surface of the polymer interlayer through melt fracture orembossing or both. The surface roughness enables and improves removal ofair during laminating of polymer interlayers to produce multiple layerglass panels, and helps to prevent the blocking of the polymerinterlayers during storage. Meanwhile, such surface roughness will alsocause the development of small scale surface variation at the interfacesbetween layers of the multilayer interlayer.

The refractive index of a substance, such as an interlayer, is themeasure of the speed of light through the substance with respect to thespeed of light in vacuum. If there is a difference between therefractive index of the layers, the result will be that the surfacevariations are visible or even more visible due to diffraction of thelight at the layer interfaces. Mottle is theoretically possible with anymultiple layer interlayer, especially where there is a sufficientlylarge difference in the refractive indices between the layers and thereis some degree of interfacial variation between the layers.

The presence of mottle in the final unitary structure of a multilayerlaminate glass panel can be problematic because a certain degree ofoptical quality is necessary in many (if not most) of the end-usecommercial applications of multilayer laminate glass panels (e.g.,vehicular, aeronautical and architectural applications). Thus, thecreation of multilayer laminate glass panels with commerciallyacceptable levels of mottle (that is, where the level of mottle is low)is paramount in the art of multiple layer glass panel manufacturing.

To ascertain the level of mottle in a laminate, the severity of themottle is assessed and categorized by a side-to-side qualitativecomparison of the shadowgraph projections for a test laminate with a setof standard laminate shadowgraphs representing a series or scale ofmottle values ranging from 1 to 4, with 1 representing a standard of lowmottle (i.e., a low number of disruptions) and 4 representing a standardof high mottle (i.e., a high number of disruptions), which is opticallyobjectionable. Based upon a visual interpretation of which standardlaminate shadowgraph picture the test shadowgraph projection bestcorresponds with, the test laminate is then placed into the mottlecategory of the corresponding standard laminate. Shadowgraph picturescan also be analyzed by digital image analysis tools to give digitalizedresults or mottle ratings.

Clarity of the multiple layer panel is another important opticalquality. Clarity is determined by measuring the level of haze in themultiple layer panel, as further described below. The level of haze mustbe very low so that the multiple layer panel is clear. In addition tohaze, there are other optical quality defects, such as visible opticaldefects in the interlayer, that cause light scattering and make thedefect visible to the eye that may cause optical distortion in the glasspanel as well. Both haze and other visible optical defects are caused bylight scattering due to the blending or mixing of materials, such asdifferent polymers or plasticizers, together, or the contamination fromsuch different polymers or plasticizers where there is a sufficientlylarge difference in the refractive index between the different polymersor plasticizers, the matrix and the contaminants, or both.

Summarized, optical quality defects such as mottle, haze and othervisible optical defects are common problems in the field of multiplelayer glass panels, particularly those used in applications whichrequire higher levels of optical or visual quality. It is now common touse a multilayer interlayer in order to provide high performancelaminates. The use of multilayer interlayers, however, has very oftenresulted in having optical defect problems, such as mottle. Accordingly,there is a need in the art for the development of an interlayer, andparticularly a multilayer interlayer, that resists or prevents theformation of mottle without a reduction in other optical, mechanical,and acoustic characteristics of a multilayer interlayer, and a need forthe development of any polymer interlayers including monolithic andmultilayer interlayers that are free from haze and other visible opticaldefects.

SUMMARY OF THE INVENTION

Because of these and other problems in the art, described herein, amongother things is a polymer interlayer comprising: a poly(vinyl butyral)resin; and at least one high refractive index plasticizer. The polymerinterlayer may be a multilayer polymer interlayer.

In an embodiment, a polymer interlayer comprises: poly(vinyl butyral)resin; and at least one high refractive index plasticizer having arefractive index of at least about 1.460; wherein the interlayercomprises about 5 to about 120 parts of the high refractive indexplasticizer mixture per 100 parts poly(vinyl butyral) resin. In anembodiment, the high refractive index plasticizer has a refractive indexof at least about 1.470. In an embodiment, the high refractive indexplasticizer has a refractive index of at least about 1.480. In anembodiment, the high refractive index plasticizer has a refractive indexof at least about 1.490. In an embodiment, the high refractive indexplasticizer has a refractive index of from about 1.460 to about 1.560.In an embodiment, the difference between the refractive index of theresin and the refractive index of the high refractive index plasticizeris less than about 0.100, or less than about 0.075. In an embodiment,the difference between the refractive index of the resin and therefractive index of the high refractive index plasticizer is less thanabout 0.050. In an embodiment, the polymer interlayer comprises at leasttwo different high refractive index plasticizers, wherein each highrefractive index plasticizer has a refractive index of at least 1.460.In an embodiment, the polymer interlayer comprises at least twodifferent plasticizers, wherein at least one plasticizer has arefractive index of at least 1.460 and wherein at least one plasticizerhas a refractive index of less than about 1.450. In an embodiment, thehigh refractive index plasticizer is selected from dipropylene glycoldibenzoate, tripropylene glycol dibenzoate, polypropylene glycoldibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycolbenzoate, propylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanedioldibenzoate, 2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate,1,3-butanediol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate,diethylene glycol di-o-toluate, triethylene glycol di-o-toluate,dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate, tri-2-ethylhexyltrimellitate, di-2-ethylhexyl terephthalate, bis-phenol Abis(2-ethylhexaonate), ethoxylated nonylphenol, and mixtures thereof. Inan embodiment, the high refractive index plasticizer is selected fromdipropylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanedioldibenzoate, and tripropylene glycol dibenzoate. In an embodiment, thepolymer interlayer further comprises a second plasticizer, wherein thesecond plasticizer is triethylene glycol di-(2-ethylhexanoate). In anembodiment, the refractive index of the polymer interlayer is at least1.480.

In an embodiment, a polymer interlayer comprises: poly(vinyl butyral)resin; and a plasticizer mixture comprising: at least one plasticizerhaving a refractive index of less than about 1.450; and at least onehigh refractive index plasticizer having a refractive index of at least1.460; wherein the refractive index of the plasticizer mixture is atleast 1.460; and wherein the interlayer comprises about 5 to about 120parts plasticizer mixture per 100 parts poly(vinyl butyral) resin. In anembodiment, the refractive index of the plasticizer mixture is at least1.480. In an embodiment, the refractive index of the polymer interlayeris at least 1.480.

In an embodiment, a polymer interlayer comprises: poly(vinyl butyral)resin; and at least one high refractive index plasticizer having arefractive index of at least about 1.460; wherein the interlayercomprises about 5 to about 120 parts of the high refractive indexplasticizer mixture per 100 parts poly(vinyl butyral) resin, and whereinthe refractive index of the polymer interlayer is at least 1.480. In anembodiment, the difference between the refractive index of the resin andthe refractive index of the high refractive index plasticizer is lessthan about 0.100, or less than about 0.075. In an embodiment, thedifference between the refractive index of the resin and the refractiveindex of the high refractive index plasticizer is less than about 0.050.In an embodiment, the polymer interlayer comprises at least twodifferent high refractive index plasticizers, wherein each highrefractive index plasticizer has a refractive index of at least 1.460.In an embodiment, the polymer interlayer comprises at least twoplasticizers, wherein at least one plasticizer has a refractive index ofat least 1.460 and wherein at least one plasticizer has a refractiveindex of less than about 1.450.

In an embodiment, a multiple layer polymer interlayer comprises:poly(vinyl butyral) resin; and at least one high refractive indexplasticizer having a refractive index of at least about 1.460; whereinthe multiple layer polymer interlayer has at least one soft layer and atleast one stiff layer, and wherein the difference between the refractiveindex of the soft layer and the stiff layer (Delta RI) is less thanabout 0.010. In embodiments, the high refractive index plasticizer has arefractive index of from about 1.460 to about 1.560. In embodiments, thesoft layer comprises a poly(vinyl butyral) resin having a residualhydroxyl content from 8 to 21 wt. %, and the stiff layer comprises apoly(vinyl butyral) resin having a residual hydroxyl content from 16 to35 wt. %, and the residual hydroxyl content between the adjacent softand stiff layers differs by at least 2 wt. %. In embodiments, the softlayer has a plasticizer content of from 10 phr to 120 phr, and the stifflayer has a plasticizer content of from 5 phr to 60 phr. In embodiments,the polymer interlayer comprises at least two different high refractiveplasticizers, wherein each high refractive plasticizer has a refractiveindex of at least 1.460. In embodiments, the polymer interlayercomprises at least two different plasticizers, wherein at least oneplasticizer has a refractive index of at least 1.460 and wherein atleast plasticizer has a refractive index of less than about 1.450. Inembodiments, the high refractive index plasticizer is selected fromdipropylene glycol dibenzoate, tripropylene glycol dibenzoate,polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexylbenzoate, diethylene glycol benzoate, propylene glycol dibenzoate,2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate, diethyleneglycol di-o-toluate, triethylene glycol di-o-toluate, dipropylene glycoldi-o-toluate, 1,2-octyl dibenzoate, tri-2-ethylhexyl trimellitate,di-2-ethylhexyl terephthalate, bis-phenol A bis(2-ethylhexaonate),ethoxylated nonylphenol, and mixtures thereof. In embodiments, the highrefractive index plasticizer is selected from dipropylene glycoldibenzoate, tripropylene glycol dibenzoate, and2,2,4-trimethyl-1,3-pentanediol dibenzoate. In embodiments, the multiplelayer polymer interlayer further comprises a second plasticizer, whereinthe second plasticizer is triethylene glycol di-(2-ethylhexanoate). Inembodiments, the multiple layer polymer interlayer further comprises asecond stiff layer, and wherein the soft layer is disposed between thestiff layers, or a second soft layer and wherein the stiff layer isdisposed between the soft layers.

In an embodiment, a polymer interlayer is disclosed, the polymerinterlayer comprising: poly(vinyl butyral) resin; and at least one highrefractive index plasticizer having a refractive index of at least about1.460; wherein the interlayer comprises about 5 to about 120 parts ofthe high refractive index plasticizer per 100 parts poly(vinyl butyral)resin. In embodiments, the multiple layer polymer interlayer has atleast one soft layer and at least one stiff layer, and wherein thedifference between the refractive index of the soft layer and the stifflayer (Delta RI) is less than about 0.010.

In embodiments, the high refractive index plasticizer has a refractiveindex of at least about 1.470, or at least about 1.480, or at leastabout 1.490, or at least about 1.500, or at least about 1.510, or atleast about 1.520.

In embodiments, the difference between the refractive index of the resinand the refractive index of the plasticizer may be less than about0.100, or less than about 0.075, or less than about 0.070, or less thanabout 0.065, or less than about 0.060, or less than about 0.055, or lessthan about 0.050, or less than about 0.040, or less than about 0.030, orless than about 0.020, or less than about 0.010, or about 0.000.

In embodiments, the polymer interlayer may comprise at least twodifferent high refractive index plasticizers, wherein each highrefractive index plasticizer has a refractive index of at least 1.460,or the polymer interlayer may comprise at least two differentplasticizers, wherein at least one plasticizer has a refractive index ofat least 1.460 and wherein at least plasticizer has a refractive indexof less than about 1.450.

In embodiments, the polymer interlayer has a refractive index of atleast 1.480, or at least 1.485.

In embodiments, the high refractive index plasticizer is selected fromdipropylene glycol dibenzoate, tripropylene glycol dibenzoate,polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexylbenzoate, diethylene glycol benzoate, propylene glycol dibenzoate,2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, diethylene glycol di-o-toluate, triethylene glycoldi-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate,tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bis-phenolA bis(2-ethylhexaonate), ethoxylated nonylphenol, and mixtures thereof,or the plasticizer may be selected from dipropylene glycol dibenzoate,2,2,4-trimethyl-1,3-pentanediol dibenzoate, and tripropylene glycoldibenzoate.

In embodiments, the polymer interlayer may further comprise anadditional plasticizer. In embodiments, the additional plasticizer istriethylene glycol di-(2-ethylhexanoate).

In embodiments, the soft layer comprises a poly(vinyl butyral) resinhaving a residual hydroxyl content from 8 to 21 wt. %, and the stifflayer comprises a poly(vinyl butyral) resin having a residual hydroxylcontent from 16 to 35 wt. %, and the residual hydroxyl content betweenthe adjacent soft and stiff layers differs by at least 2 wt. %.

In another embodiment, a multiple layer polymer interlayer comprises:poly(vinyl butyral) resin; and a plasticizer mixture comprising: atleast one plasticizer selected from the group consisting of: triethyleneglycol di-(2-ethylhexanoate), triethylene glycol di-(2-ethylbutyrate),triethylene glycol diheptanoate, tetraethylene glycol diheptanoate,tetraethylene glycol di-(2-ethylhexanoate), dihexyl adipate, dioctyladipate, hexyl cyclohexyladipate, diisononyl adipate, heptylnonyladipate, di(butoxyethyl) adipate, bis(2-(2-butoxyethoxy)ethyl) adipate,dibutyl sebacate, and dioctyl sebacate; and at least one high refractiveindex plasticizer having a refractive index of at least 1.460; whereinthe refractive index of the plasticizer mixture is at least 1.460;wherein the multiple layer polymer interlayer has at least one softlayer and at least one stiff layer, and wherein the difference betweenthe refractive index (Delta RI) of the soft layer and the stiff layer isless than about 0.010. In embodiments, the plasticizer mixture has arefractive index of from about 1.460 to about 1.560. In embodiments, thesoft layer comprises a poly(vinyl butyral) resin having a residualhydroxyl content from 8 to 21 wt. %, and the stiff layer comprises apoly(vinyl butyral) resin having a residual hydroxyl content from 16 to35 wt. %, and the residual hydroxyl content between the adjacent softand stiff layers differs by at least 2 wt. %. In embodiments, the softlayer has a plasticizer content of from 10 phr to 120 phr, and the stifflayer has a plasticizer content of from 5 phr to 60 phr. In embodiments,the high refractive index plasticizer is selected from dipropyleneglycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycoldibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycolbenzoate, propylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanedioldibenzoate, 2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate,1,3-butanediol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate,diethylene glycol di-o-toluate, triethylene glycol di-o-toluate,dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate, tri-2-ethylhexyltrimellitate, di-2-ethylhexyl terephthalate, bis-phenol Abis(2-ethylhexaonate), ethoxylated nonylphenol, and mixtures thereof. Inembodiments, the multiple layer polymer interlayer further comprises asecond stiff layer, and wherein the soft layer is disposed between thestiff layers or a second soft layer and wherein the stiff layer isdisposed between the soft layers.

In another embodiment, a multiple layer polymer interlayer comprises:poly(vinyl butyral) resin; and at least one high refractive indexplasticizer having a refractive index of at least about 1.460; whereinthe multiple layer polymer interlayer has at least one soft layer and atleast two stiff layers wherein the soft layer is disposed between thestiff layers, and wherein the difference between the refractive index ofthe soft layer and the stiff layers is less than about 0.010. Inembodiments, the soft layer comprises a poly(vinyl butyral) resin havinga residual hydroxyl content from 8 to 21 wt. %, and the stiff layercomprises a poly(vinyl butyral) resin having a residual hydroxyl contentfrom 16 to 35 wt. %, and the residual hydroxyl content between theadjacent soft and stiff layers differs by at least 2 wt. %. Inembodiments, the soft layer has a plasticizer content of from 10 phr to120 phr, and the stiff layer has a plasticizer content of from 5 phr to60 phr. In embodiments, the polymer interlayer comprises at least twodifferent high refractive index plasticizers, wherein each highrefractive index plasticizer has a refractive index of at least 1.460.

In another embodiment, a multiple layer polymer interlayer comprises:poly(vinyl butyral) resin; and at least one high refractive indexplasticizer having a refractive index of at least about 1.460; whereinthe multiple layer polymer interlayer has at least one soft layer and atleast one stiff layer, and wherein the difference between the refractiveindex of the soft layer and the stiff layer (Delta RI) is less thanabout 0.010.

In another embodiment, a polymer interlayer comprising: poly(vinylbutyral) resin; and a plasticizer mixture comprising: at least oneplasticizer selected from the group consisting of: triethylene glycoldi-(2-ethylhexanoate), triethylene glycol di-(2-ethylbutyrate),triethylene glycol diheptanoate, tetraethylene glycol diheptanoate,tetraethylene glycol di-(2-ethylhexanoate), dihexyl adipate, dioctyladipate, hexyl cyclohexyladipate, diisononyl adipate, heptylnonyladipate, dibutyl sebacate, dioctyl sebacate; and at least one highrefractive index plasticizer having a refractive index of at least1.460; wherein the refractive index of the plasticizer mixture is atleast 1.460; and wherein the interlayer comprises about 5 to about 120parts plasticizer mixture per 100 parts poly(vinyl butyral) resin isdisclosed. In embodiments, the high refractive index plasticizer has arefractive index of at least about 1.470, or at least about 1.480, or atleast about 1.490, or at least about 1.500, or at least about 1.510, orat least about 1.520. In embodiments, the refractive index of theplasticizer mixture is at least about 1.470, or at least about 1.480, orat least about 1.490. In embodiments, the polymer interlayer has arefractive index of at least 1.480, or at least 1.485. In embodiments,at least one plasticizer is triethylene glycol di-(2-ethylhexanoate). Incertain embodiments, the high refractive index plasticizer is selectedfrom dipropylene glycol dibenzoate, tripropylene glycol dibenzoate,polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexylbenzoate, diethylene glycol benzoate, propylene glycol dibenzoate,2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, diethylene glycol di-o-toluate, triethylene glycoldi-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate,tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bis-phenolA bis(2-ethylhexaonate), ethoxylated nonylphenol, and mixtures thereof,or the high refractive index plasticizer is selected from dipropyleneglycol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate, andtripropylene glycol dibenzoate, or one plasticizer is triethylene glycoldi-(2-ethylhexanoate) and the high refractive index plasticizer isselected from dipropylene glycol dibenzoate,2,2,4-trimethyl-1,3-pentanediol dibenzoate, and tripropylene glycoldibenzoate.

A multiple layer polymer interlayer comprising: poly(vinyl butyral)resin; and at least one high refractive index plasticizer having arefractive index of at least about 1.460; wherein the multiple layerpolymer interlayer has at least one soft layer and at least one stifflayer, and wherein the difference between the refractive index of thesoft layer and the stiff layer is less than about 0.010 is alsodisclosed. In embodiments, the difference between the refractive indexof the soft layer and the stiff layer is less than about 0.009, lessthan about 0.008, less than about 0.007, less than about 0.006, lessthan about 0.005, less than about 0.004, less than about 0.003, lessthan about 0.002, less than about 0.001, or about 0.000. The plasticizermay have a refractive index of at least about 1.470, or at least about1.480, or at least about 1.490, or at least about 1.500, or at leastabout 1.510, or at least about 1.520. In embodiments, the polymerinterlayer has a refractive index of at least 1.480. In embodiments, thepolymer interlayer comprises at least two different high refractiveindex plasticizers, wherein each high refractive index plasticizer has arefractive index of at least 1.460, or the polymer interlayer comprisesat least two different plasticizers, wherein at least one plasticizerhas a refractive index of at least 1.460 and wherein at least oneplasticizer has a refractive index of less than about 1.450. The highrefractive index plasticizer may be selected from dipropylene glycoldibenzoate, tripropylene glycol dibenzoate, polypropylene glycoldibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycolbenzoate, propylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanedioldibenzoate, 2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate,1,3-butanediol dibenzoate, diethylene glycol di-o-toluate, triethyleneglycol di-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyldibenzoate, tri-2-ethylhexyl trimellitate, di-2-ethylhexylterephthalate, bis-phenol A bis(2-ethylhexaonate), ethoxylatednonylphenol, and mixtures thereof, or the high refractive indexplasticizer may be selected from dipropylene glycol dibenzoate,2,2,4-trimethyl-1,3-pentanediol dibenzoate, and tripropylene glycoldibenzoate. In an embodiment, the polymer interlayer may furthercomprise an additional plasticizer. In an embodiment, the additionalplasticizer is triethylene glycol di-(2-ethylhexanoate). In anembodiment, the polymer interlayer may further comprise a second stifflayer, and wherein the soft layer is disposed between the two stifflayers. In an embodiment, the polymer interlayer may further comprise asecond soft layer, wherein the stiff layer is disposed between the twosoft layers. In embodiments, the polymer interlayer may compriseadditional soft and/or stiff layers.

In another embodiment, a multiple layer polymer interlayer is disclosed,the multiple layer polymer interlayer comprising: poly(vinyl butyral)resin; and a plasticizer mixture comprising: at least one plasticizerselected from the group consisting of: triethylene glycoldi-(2-ethylhexanoate), triethylene glycol di-(2-ethylbutyrate),triethylene glycol diheptanoate, tetraethylene glycol diheptanoate,tetraethylene glycol di-(2-ethylhexanoate), dihexyl adipate, dioctyladipate, hexyl cyclohexyladipate, diisononyl adipate, heptylnonyladipate, dibutyl sebacate, dioctyl sebacate, di(butoxyethyl) adipate,and bis(2-(2-butoxyethoxy)ethyl) adipate; and at least one highrefractive index plasticizer having a refractive index of at least1.460; wherein the refractive index of the plasticizer mixture is atleast about 1.460; wherein the multiple layer polymer interlayer has atleast one soft layer and at least one stiff layer, and wherein thedifference between the refractive index of the soft layer and the stifflayer is less than about 0.010. The difference between the refractiveindex of the soft layer and the stiff layer may be less than about0.009, less than about 0.008, less than about 0.007, less than about0.006, less than about 0.005, less than about 0.004, less than about0.003, less than about 0.002, less than about 0.001, or about 0.000. Inan embodiment, the polymer interlayer may further comprise a secondstiff layer, and wherein the soft layer is disposed between the twostiff layers. In an embodiment, the polymer interlayer may furthercomprise a second soft layer, wherein the stiff layer is disposedbetween the two soft layers. In embodiments, the polymer interlayer maycomprise additional soft and/or stiff layers.

In another embodiment, a multiple layer polymer interlayer comprises:poly(vinyl butyral) resin; and at least one high refractive indexplasticizer having a refractive index of at least about 1.460; whereinthe multiple layer polymer interlayer has at least one soft layer and atleast two stiff layers wherein the soft layer is disposed between thestiff layers, and wherein the difference between the refractive index ofthe soft layer and the stiff layers is less than about 0.010. Inembodiments, the soft layer comprises a poly(vinyl butyral) resin havinga residual hydroxyl content from 8 to 21 wt. %, and the stiff layercomprises a poly(vinyl butyral) resin having a residual hydroxyl contentfrom 16 to 35 wt. %, and the residual hydroxyl content between theadjacent soft and stiff layers differs by at least 2 wt. %. Inembodiments, the soft layer has a plasticizer content of from 10 phr to120 phr, and the stiff layer has a plasticizer content of from 5 phr to60 phr. In embodiments, the polymer interlayer comprises at least twodifferent high refractive index plasticizers, wherein each highrefractive index plasticizer has a refractive index of at least 1.460.

In an embodiment, a multiple layer polymer interlayer comprises: a firstlayer comprising poly(vinyl butyral) resin and a first plasticizer; asecond layer comprising poly(vinyl butyral) resin and a secondplasticizer; and a third layer comprising poly(vinyl butyral) resin anda third plasticizer disposed between the first layer and the secondlayer; and wherein at least one of the first, second and thirdplasticizers is a high refractive index plasticizer having a refractiveindex of at least about 1.460; wherein at least one layer is a softlayer and at least one layer is a stiff layer, and wherein thedifference between the refractive index of the soft layer and the stifflayer (Delta RI) is less than about 0.010. In an embodiment, the highrefractive index plasticizer has a refractive index of from about 1.460to about 1.560. In an embodiment, the soft layer comprises a poly(vinylbutyral) resin having a residual hydroxyl content from 8 to 21 wt. %,and the stiff layer comprises a poly(vinyl butyral) resin having aresidual hydroxyl content from 16 to 35 wt. %, and the residual hydroxylcontent between the adjacent soft and stiff layers differs by at least 2wt. %. In an embodiment, the soft layer has a plasticizer content offrom 10 phr to 120 phr, and the stiff layer has a plasticizer content offrom 5 phr to 60 phr. In an embodiment, the multiple layer interlayercomprises at least two different high refractive plasticizers, whereineach high refractive index plasticizer has a refractive index of atleast 1.460. In an embodiment, the at least two high refractiveplasticizers are in the same layer. In another embodiment, the at leasttwo high refractive plasticizers are in different layers. In anembodiment, the multilayer interlayer comprises at least two differentplasticizers, wherein at least one plasticizer has a refractive index ofat least 1.460 and wherein at least one plasticizer has a refractiveindex of less than about 1.450. In an embodiment, the first and secondlayers comprise at least one plasticizer having a refractive index of atleast 1.460, and wherein the third layer comprises at least oneplasticizer having a refractive index of less than 1.450. In anembodiment, the third layer comprises at least one plasticizer having arefractive index of at least 1.460, and wherein the first and secondlayers comprise at least one plasticizer having a refractive index ofless than 1.450. In an embodiment, the first and second layers are stifflayers, and wherein the third layer is a soft layer. In an embodiment,the first and second layers are soft layers, and wherein the third layeris a stiff layer.

In an embodiment, a multiple layer polymer interlayer comprises: a firstlayer comprising poly(vinyl butyral) resin and a first plasticizer; asecond layer comprising poly(vinyl butyral) resin and a secondplasticizer; and a third layer comprising poly(vinyl butyral) resin anda third plasticizer disposed between the first layer and the secondlayer; wherein at least one of the first, second and third plasticizersis a mixture comprising: at least one plasticizer having a refractiveindex of less than about 1.450; and at least one high refractive indexplasticizer having a refractive index of at least 1.460; wherein therefractive index of the plasticizer mixture is at least 1.460; whereinat least one of the layers is a soft layer and at least one of thelayers is a stiff layer, and wherein the difference between therefractive index (Delta RI) of the soft layer and the stiff layer isless than about 0.010. In an embodiment, the plasticizer mixture has arefractive index of from about 1.460 to about 1.560. In an embodiments,the soft layer comprises a poly(vinyl butyral) resin having a residualhydroxyl content from 8 to 21 wt. %, and the stiff layer comprises apoly(vinyl butyral) resin having a residual hydroxyl content from 16 to35 wt. %, and the residual hydroxyl content between the adjacent softand stiff layers differs by at least 2 wt. %. In an embodiment, the softlayer has a plasticizer content of from 10 phr to 120 phr, and the stifflayer has a plasticizer content of from 5 phr to 60 phr.

In an embodiment, a multiple layer polymer interlayer comprises: a firststiff layer comprising poly(vinyl butyral) resin and a firstplasticizer, wherein the first plasticizer is present in an amount offrom 5 phr to 60 phr; a second stiff layer comprising poly(vinylbutyral) resin and a second plasticizer, wherein the second plasticizeris present in an amount of from 5 phr to 60 phr; and a first soft layercomprising poly(vinyl butyral) resin and a third plasticizer, whereinthe third plasticizer is present in an amount of from 10 phr to 120 phr,and wherein the first soft layer is disposed between the first stifflayer and the second stiff layer; wherein at least one of the first,second and third plasticizers is a high refractive index plasticizerhaving a refractive index of at least about 1.460; wherein thedifference between the refractive index of the soft layer and the stifflayers is less than about 0.010. In embodiments, the soft layercomprises a poly(vinyl butyral) resin having a residual hydroxyl contentfrom 8 to 21 wt. %, and the stiff layer comprises a poly(vinyl butyral)resin having a residual hydroxyl content from 16 to 35 wt. %, and theresidual hydroxyl content between the adjacent soft and stiff layersdiffers by at least 2 wt. %. In embodiments, the polymer interlayercomprises at least two different high refractive index plasticizers,wherein each high refractive index plasticizer has a refractive index ofat least 1.460. In embodiments, the multilayer interlayer comprises atleast two different plasticizers, wherein at least one plasticizer has arefractive index of at least 1.460 and wherein at least one plasticizerhas a refractive index of less than about 1.450.

A multiple layer panel is also disclosed. The multiple layer panelcomprises at least one rigid substrate, and a polymer interlayer ormultiple layer polymer interlayer as disclosed herein. The panel hasimproved optical properties.

A method of making a polymer interlayer is also disclosed, wherein themultilayer interlayer comprises a poly(vinyl butyral) resin and at leastone high refractive index plasticizer, as disclosed herein. The polymerinterlayer may be a multiple layer polymer interlayer.

In certain embodiments, the rigid substrate is glass. In otherembodiments, the panel may further comprise a photovoltaic cell, withthe interlayer encapsulating the photovoltaic cell.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Described herein, among other things, are interlayers comprised of athermoplastic resin, at least one high refractive index plasticizer, andoptionally a conventional plasticizer, wherein the interlayers haveimproved optical quality. Also described are multiple layer glass panelscomprising the interlayers, and methods of making the polymerinterlayers. The use of a thermoplastic resin, and at least one highrefractive index plasticizer having a refractive index of at least about1.460, or at least about 1.470, or greater than about 1.470, or at leastabout 1.480, or greater than about 1.480, or at least about 1.490, orgreater than about 1.490, or at least about 1.500, or greater than about1.500, or at least about 1.510, or greater than 1.520, creates aninterlayer having decreased mottle and/or low haze without sacrificingother characteristics. In this regard, the use of at least one highrefractive index plasticizer or combination of plasticizers, whenselected to have a certain refractive index compared to interlayerscomprising only conventional plasticizer, and the resin and otheradditives, results in an interlayer having excellent optical propertiesas measured by at least mottle and haze. As a result, higher quality,optically clear multiple layer glass panels are produced, less scrap oroff grade material is generated, and operational efficiency is improved.As noted here, the refractive index (also known as index of refraction)of a plasticizer or a resin used in the entirety of this disclosure iseither measured in accordance with ASTM D542 at a wavelength of 589 nmand 25° C. or reported in literature in accordance with the ASTM D542.

Multilayer interlayers, such as an interlayer having two or more layers(such as a trilayer interlayer having three layers), often comprise atleast one soft layer and at least one stiff layer. The soft layer(s) isoften the inner or core layer in interlayers having at least threelayers. The soft core layer(s) may be specifically designed for acousticattenuation, and the polymer interlayer may have stiffer skin or outerlayers. In the interlayer comprising poly(vinyl butyral) (“PVB”) resinand plasticizer, it has been common that plasticizer is selected thegroup of triethylene glycol di-(2-ethylhexanoate) (“3GEH”), triethyleneglycol di-(2-ethylbutyrate), triethylene glycol diheptanoate,tetraethylene glycol diheptanoate, tetraethylene glycoldi-(2-ethylhexanoate), dihexyl adipate, dioctyl adipate, hexylcyclohexyladipate, diisononyl adipate, heptylnonyl adipate, dibutylsebacate, dioctyl sebacate, di(butoxyethyl) adipate, andbis(2-(2-butoxyethoxy)ethyl) adipate, and mixtures thereof. Theseplasticizers have refractive indices of 1.442 to 1.449. As used herein,the plasticizer having a refractive index of about 1.450 or less isreferred as “conventional plasticizer”. 3GEH (refractive index=1.442) isthe most common plasticizer present in interlayers manufactured forvarious properties and applications. In the multilayer interlayer havingconventional plasticizer, the plasticizer (such as triethylene glycoldi-(2-ethylhexanoate) (3GEH)) in the core and skin layers oftenpartitions (as it reaches equilibrium state) in favor of the softerlayer over the stiffer or harder layer, in a proportion predominated bythe characteristics of the particular resins used in the skin and corelayers. Because PVB resin has a refractive index of approximately 1.485to 1.495, and because more plasticizer ends up in the softer layer thanin the stiffer layer, the softer layer has a different, and lower,refractive index than the stiffer layer, creating a refractive index(“RI”) difference (“Delta RI”) between the layers. It has beendetermined that this difference in refractive index contributes to anundesirable optical defect known as mottle or the mottle defect.

Some terminology used throughout this application will be explained toprovide a better understanding of the invention. The terms “polymerinterlayer sheet,” “interlayer,” and “polymer melt sheet” as usedherein, generally may designate a single-layer sheet or a multilayeredinterlayer. A “single-layer sheet,” as the name implies, is a singlepolymer layer extruded as one layer. A multilayered interlayer, on theother hand, may comprise multiple layers, including separately extrudedlayers, co-extruded layers, or any combination of separately andco-extruded layers. Thus the multilayered interlayer could comprise, forexample: two or more single-layer sheets combined together(“plural-layer sheet”); two or more layers co-extruded together(“co-extruded sheet”); two or more co-extruded sheets combined together;a combination of at least one single-layer sheet and at least oneco-extruded sheet; a combination of a single-layer sheet and aplural-layer sheet; and a combination of at least one plural-layer sheetand at least one co-extruded sheet. In various embodiments of thepresent disclosure, a multilayered interlayer comprises at least twopolymer layers (e.g., a single layer or multiple layers co-extrudedand/or laminated together) disposed in direct contact with each other,wherein each layer comprises a polymer resin, as detailed more fullybelow. As used herein for multilayer interlayers having at least threelayers, “skin layer” generally refers to the outer layers of theinterlayer and “core layer” generally refers to the inner layer(s).Thus, one exemplary embodiment would be: skin layer//core layer//skinlayer. As used herein, “stiff layer” or “stiffer layer” generally refersto a layer that is stiffer or more rigid than another layer and that hasa glass transition temperature that is generally at least two degrees C.(2° C.) higher than another layer. As used herein, the “soft layer” or“softer layer” generally refers to a layer that is softer than anotherlayer and that has a glass transition temperature that is generally atleast two degrees C. (2° C.) lower than another layer. The soft layerand stiff layer can be differentiated when both layers contain the sameplasticizer and each has a plasticizer loading of 30 phr. The soft layerand stiff layer can be further differentiated when the soft and stifflayers are in contact with each other and the plasticizer partitions toreach equilibrium state between the layers. Of course, thisdifferentiation can also be made at other plasticizer loadings as longas the loadings are within limits of compatibility of the plasticizer toresins. In the multilayer interlayers having skin layer//corelayer//skin layer configuration, in some embodiments the skin layermaybe stiffer and the core layer may be softer, while in otherembodiments the skin layer may be softer and the core layer may bestiffer. It should be noted, however, further embodiments includeinterlayers having only two layers or interlayers having more than threelayers (e.g., 4, 5, 6, or up to 10 or more individual layers).Additionally, any multilayer interlayer utilized can be varied bymanipulating the composition, thickness, or positioning of the layersand the like. For example, in one trilayer polymer interlayer sheet, thetwo stiff (or outer or skin) layers may comprise poly(vinyl butyral)(“PVB”) resin with a plasticizer or mixture of plasticizers, while thesofter (inner or core) layers may comprise the same or different PVBresin or a different thermoplastic material with a the same or differentplasticizer and/or mixture of plasticizers. Thus, it is contemplatedthat the stiff or skin layers and the soft or core layer(s) of themultilayered interlayer sheets may be comprised of the samethermoplastic material or different thermoplastic materials and the sameor different plasticizer or plasticizers. Either or both layers mayinclude additional additives as known in the art, as desired. Inmultilayer interlayers, the plasticizers or mixture of plasticizers inthe stiff or skin and soft or core layers are selected such that thedifference in refractive indices of the stiff or skin layer(s) and softor core layer(s) is minimized, and the mottle is reduced. For example,in some embodiments, the difference between the refractive index of thesoft or core layer(s) and the refractive index of the stiff or skinlayer(s) (Delta RI) may be less than 0.010, or less than 0.009, or lessthan 0.008, or less than 0.007, or less than 0.006, or less than 0.005,or less than 0.004, or less than 0.003, or less than 0.002, or less than0.001, or even about 0.000. The Delta RI may be positive or negative, ormay be taken as the absolute value of the difference between the layers.In some embodiments, the difference between the refractive index of theresin and the refractive index of the plasticizer (Delta RI) may be lessthan 0.100, or less than 0.075, or less than 0.070, or less than 0.065,or less than 0.060, or less than 0.055, or less than 0.050, or less than0.040, or less than 0.030, or less than 0.020, or less than 0.010, orabout 0.000.

Although the embodiments described below refer to the polymer resin asbeing PVB, it would be understood by one of ordinary skill in the artthat the polymer may be any polymer suitable for use in a multiple layerpanel. Typical polymers include, but are not limited to, polyvinylacetals (PVA) (such as poly(vinyl butyral) (PVB)), polyurethane (PU),poly(ethylene-co-vinyl acetate) (EVA), polyvinylchloride (PVC),poly(vinylchloride-co-methacrylate), polyethylenes, polyolefins,ethylene acrylate ester copolymers, poly(ethylene-co-butyl acrylate),silicone elastomers, epoxy resins, and acid copolymers such asethylene/carboxylic acid copolymers and its ionomers, derived from anyof the foregoing possible thermoplastic resins, combinations of theforegoing, and the like. PVB, polyvinyl chloride, and polyurethane areuseful polymers generally for interlayers; PVB is particularly usefulwhen used in conjunction with the interlayers of this disclosurecomprising high refractive index plasticizers.

Prior to discussing the addition of the specific plasticizer orplasticizers selected to produce the interlayer having improved opticalquality, some common components found in an interlayer, both generallyand in interlayers of the present disclosure, and the formation thereof,will be discussed.

The PVB resin is produced by known aqueous or solvent acetalizationprocesses by reacting polyvinyl alcohol (“PVOH”) with butyraldehyde inthe presence of an acid catalyst, separation, stabilization, and dryingof the resin. Such acetalization processes are disclosed, for example,in U.S. Pat. Nos. 2,282,057 and 2,282,026 and Vinyl Acetal Polymers, inEncyclopedia of Polymer Science & Technology, 3rd edition, Volume 8,pages 381-399, by B. E. Wade (2003), the entire disclosures of which areincorporated herein by reference. The resin is commercially available invarious forms, for example, as Butvar® Resin from Solutia Inc., a whollyowned subsidiary of Eastman Chemical Company.

As used herein, residual hydroxyl content (calculated as % PVOH byweight) in PVB refers to the amount of hydroxyl groups remaining on thepolymer chains after processing is complete. For example, PVB can bemanufactured by hydrolyzing poly(vinyl acetate) to PVOH, and thenreacting the PVOH with butyraldehyde. In the process of hydrolyzing thepoly(vinyl acetate), typically not all of the acetate side groups areconverted to hydroxyl groups. Further, reaction with butyraldehydetypically will not result in all hydroxyl groups being converted toacetal groups. Consequently, in any finished PVB resin, there typicallywill be residual acetate groups (as vinyl acetate groups) and residualhydroxyl groups (as vinyl hydroxyl groups) as side groups on the polymerchain. As used herein, residual hydroxyl content is measured on a weightpercent basis per ASTM 1396.

In various embodiments, the PVB resin comprises about 8 to about 35weight percent (wt. %) hydroxyl groups calculated as % PVOH, about 13 toabout 30 wt. %, about 8 to about 22 wt. %, or about 15 to about 22 wt.%; and, for certain embodiments, about 17.75 to about 19.85 wt. %hydroxyl groups calculated as % PVOH. The resin can also comprise lessthan 25 wt. % residual ester groups, less than 20 wt. % residual estergroups, less than 15 wt. % residual ester groups, less than 13 wt. %,less than 11 wt. %, less than 9 wt. %, less than 7 wt. %, less than 5wt. %, or less than 1 wt. % residual ester groups calculated aspolyvinyl ester, e.g., acetate, with the balance being an acetal, suchas butyraldehyde acetal, but optionally being other acetal groups, suchas a 2-ethyl hexanal acetal group, or a mix of butyraldehyde acetal and2-ethyl hexanal acetal groups.

In various embodiments, where the interlayer is a multilayer interlayersuch as a trilayer, the residual hydroxyl contents of the PVB resinsused in the stiff (or skin) layer(s) and soft (or core) layer(s) can bedifferent to provide certain performance characteristics. The resin forthe soft layer(s), for example, can comprise about 8 to about 21 wt. %,about 8 to about 18 wt. %, or about 8 to about 16 wt. %, or about 8 toabout 14 wt. % residual hydroxyl groups calculated as % PVOH. The resinfor the stiff layer(s), for example, can comprise about 13 to about 35wt. %, about 16 to about 35 wt. %, or about 15 to about 22 wt. %; and,for certain embodiments, about 17.25 to about 22.25 wt. % residualhydroxyl groups calculated as % PVOH. In various embodiments, theresidual hydroxyl content of adjacent stiff and soft layers can differby at least 2 wt. %, or at least 4 wt. %, or at least 6 wt. %, or atleast 8 wt. %, or at least by 10 wt. %. The resin for the soft layer(s)or for the stiff layer(s) or for both the soft layer(s) and stifflayer(s) can also comprise less than 25 wt. % residual ester groups,less than 20 wt. % residual ester groups, less than 15 wt. %, less than13 wt. %, less than 11 wt. %, less than 9 wt. %, less than 7 wt. %, lessthan 5 wt. %, or less than 1 wt. % residual ester groups calculated aspolyvinyl ester, e.g., acetate, with the balance being an acetal, suchas butyraldehyde acetal, but optionally being other acetal groups, suchas a 2-ethyl hexanal acetal group, or a mix of butyraldehyde acetal and2-ethyl hexanal acetal groups, as previously discussed.

In various embodiments, where the interlayer is a multilayer interlayersuch as a trilayer, the skin layer(s) could have higher residualhydroxyl groups calculated as % PVOH than the core layer(s), or the skinlayer(s) could be stiffer than the core layer(s); in other embodiments,the skin layer(s) could have lower residual hydroxyl groups calculatedas % PVOH than the core layer(s), or the skin layer(s) could be softer.If there are more than two or three layers, any combination ofstiff/soft/stiff/soft, such as soft/stiff/soft/stiff,soft/stiff/stiff/soft, stiff/soft/soft/stiff, and any number of layers,may be used, depending on the desired properties and application.

For a given type of plasticizer, the compatibility of the plasticizer inthe PVB polymer is largely determined by the hydroxyl content of thepolymer. PVB with greater residual hydroxyl content is typically, butnot always, correlated with reduced plasticizer compatibility orcapacity, i.e., less plasticizer could be incorporated. Conversely, PVBwith a lower residual hydroxyl content typically, but not always, willresult in increased plasticizer compatibility or capacity, i.e., moreplasticizer could be incorporated. For some plasticizer types, suchcorrelation might be reversed. Generally, this correlation between theresidual hydroxyl content of a polymer and plasticizercompatibility/capacity will allow for the addition of the proper amountof plasticizer to the polymer resin and more importantly to stablymaintain differences in plasticizer content between multiple layers.

The PVB resin (or resins) of the present disclosure typically has amolecular weight of greater than 50,000 Daltons, or less than 500,000Daltons, or about 50,000 to about 500,000 Daltons, or about 70,000 toabout 500,000 Daltons, or more preferably about 100,000 to about 425,000Daltons, as measured by size exclusion chromatography using low anglelaser light scattering. As used herein, the term “molecular weight”means the weight average molecular weight.

Various adhesion control agents (“ACAs”) can be used in the interlayersof the present disclosure to control the adhesion of the interlayersheet to glass. In various embodiments of interlayers of the presentdisclosure, the interlayer can comprise about 0.003 to about 0.15 partsACAs per 100 parts resin; about 0.01 to about 0.10 parts ACAs per 100parts resin; and about 0.01 to about 0.04 parts ACAs per 100 partsresin. Such ACAs, include, but are not limited to, the ACAs disclosed inU.S. Pat. No. 5,728,472 (the entire disclosure of which is incorporatedherein by reference), residual sodium acetate, potassium acetate,magnesium bis(2-ethyl butyrate), and/or magnesium bis(2-ethylhexanoate).

Other additives may be incorporated into the interlayer to enhance itsperformance in a final product and impart certain additional propertiesto the interlayer. Such additives include, but are not limited to, dyes,pigments, stabilizers (e.g., ultraviolet stabilizers), antioxidants,anti-blocking agents, flame retardants, IR absorbers or blockers (e.g.,indium tin oxide, antimony tin oxide, lanthanum hexaboride (LaB₆) andcesium tungsten oxide), processing aides, flow enhancing additives,lubricants, impact modifiers, nucleating agents, thermal stabilizers, UVabsorbers, dispersants, surfactants, chelating agents, coupling agents,adhesives, primers, reinforcement additives, and fillers, among otheradditives known to those of ordinary skill in the art.

In various embodiments of interlayers of the present disclosure, theinterlayer can comprise 0 to about 100 or more, 0 to about 80, about 0to 45, about 10 to about 75, about 15 to about 60, about 15 to about 50,about 25 to about 50, about 10 to about 40, about 15 to about 40, about25 to about 38, about 29 to about 32, and about 30 phr (parts perhundred parts resin) conventional plasticizer. Of course, otherquantities can be used as is appropriate for the particular applicationand the desired properties.

In various embodiments of interlayers of the present disclosure, theinterlayer comprises greater than 5 phr, about 5 to about 120 phr, about5 to 100, about 10 to about 80 phr, about 20 to about 70 phr, about 30to about 60 phr, or less than 120 phr, or less than 110 phr, or lessthan 100 phr, or less than 90 phr, or less than 80 phr, or less than 70phr, or less than 60 phr total plasticizer. While the total plasticizercontent is indicated above, the plasticizer content in the skin layer(s)or core layer(s) can be different from the total plasticizer content. Inaddition, the skin layer(s) and core layer(s) can have differentplasticizer types and plasticizer contents, in the ranges previouslydiscussed, as each respective layer's plasticizer content at theequilibrium state is determined by the layer's respective residualhydroxyl contents, as disclosed in U.S. Pat. No. 7,510,771 (the entiredisclosure of which is incorporated herein by reference). For example,at equilibrium the interlayer could comprise two skin layers, each with38 phr plasticizer, and a core layer with 75 phr plasticizer, for atotal plasticizer amount for the interlayer of about 54.3 phr when thecombined skin layer thickness equals that of the core layer. As usedherein, the amount of plasticizer, or any other component in theinterlayer, can be measured as parts per hundred parts resin (phr), on aweight per weight basis. For example, if 30 grams of plasticizer isadded to 100 grams of polymer resin, then the plasticizer content of theresulting plasticized polymer would be 30 phr. As used herein, when theplasticizer content of the interlayer is given, the plasticizer contentis determined with reference to the phr of the plasticizer in the mix ormelt that was used to produce the interlayer. In embodiments of amultilayer interlayer having a stiff layer and a soft layer, the stifflayer may have from 5 to 60 phr plasticizer and the soft layer may havefrom 10 to 120 phr plasticizer.

In some embodiments, the conventional plasticizer includes, for example,triethylene glycol di-(2-ethylhexanoate) (“3GEH”), triethylene glycoldi-(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethyleneglycol diheptanoate, tetraethylene glycol di-(2-ethylhexanoate), dihexyladipate, dioctyl adipate, hexyl cyclohexyladipate, diisononyl adipate,heptylnonyl adipate, dibutyl sebacate, dioctyl sebacate, di(butoxyethyl)adipate, bis(2-(2-butoxyethoxy)ethyl) adipate, and mixtures thereof. Insome embodiments, the conventional plasticizer is 3GEH.

Increasing the refractive index of one or more of the layers, such as asoft or core layer, to be closer to the refractive index of the otherlayer(s) can minimize the difference in refractive index between thelayers (such as the stiff (or skin) and soft (or core) layers), therebyminimizing the amount of mottle in the multilayer interlayer. One way toincrease the refractive index of one of the layers is to use a highrefractive index plasticizer. As used herein, a “high refractive indexplasticizer” is a plasticizer having a refractive index of at leastabout 1.460. The refractive index of one conventional and commonly usedplasticizer, such as 3GEH, is about 1.442. The refractive indices of theconventional plasticizers listed above are from about 1.442 to about1.449. Examples of plasticizers having a high refractive index that maybe used include, but are not limited to, polyadipates (RI of about 1.460to about 1.485); epoxides such as epoxidized soybean oils (RI of about1.460 to about 1.480); phthalates and terephthalates (RI of about 1.480to about 1.540); benzoates (RI of about 1.480 to about 1.550); and otherspecialty plasticizers (RI of about 1.490 to about 1.520). Therefractive index of poly(vinyl butyral) resin is approximately 1.485 to1.495.

Examples of the high refractive index plasticizer include, but are notlimited to, esters of a polybasic acid or a polyhydric alcohol,polyadipates, epoxides, phthalates, terephthalates, benzoates, toluates,mellitates and other specialty plasticizers, among others. Examples ofsuitable plasticizers include, but are not limited to, dipropyleneglycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycoldibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycolbenzoate, propylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanedioldibenzoate, 2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate,1,3-butanediol dibenzoate, diethylene glycol di-o-toluate, triethyleneglycol di-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyldibenzoate, tri-2-ethylhexyl trimellitate, di-2-ethylhexylterephthalate, bis-phenol A bis(2-ethylhexaonate), ethoxylatednonylphenol, and mixtures thereof. In some embodiments, examples of highrefractive index plasticizers are dipropylene glycol dibenzoate,2,2,4-trimethyl-1,3-pentanediol dibenzoate, and tripropylene glycoldibenzoate.

In multilayer interlayers, comprising, for example, stiff and softlayers, the stiff and soft layers could each comprise a conventionalplasticizer in combination with a one or more high refractive indexplasticizer, or comprise a single high refractive index plasticizeralone or a combination of high refractive index plasticizers, so long asthe difference in the refractive indices (Delta RI) between layers isminimized. Concentrations of the plasticizers incorporated into themelts of the different layers, such as the soft or stiff layers, are asdescribed above.

In any of these embodiments, the plasticizer(s) can be any of thosedescribed above. In embodiments, the plasticizer(s) is selected suchthat the Delta RI between the layers of the interlayer is minimized(that is, as close to 0.000 as possible), or less than 0.010, or lessthan 0.009, or less than 0.008, or less than 0.007, or less than 0.006,or less than 0.005, or less than 0.004, or less than 0.003, or less than0.002, or less than 0.001, or about 0.000. In other embodiments, theplasticizer is selected such that the Delta RI between the resin andplasticizer is less than 0.075, or less than 0.070, or less than about0.065, or less than 0.060, or less than 0.055, or less than 0.050, orless than 0.040, or less than 0.030, or less than 0.020, or less than0.010, or about 0.000. In various embodiments, the high refractive indexplasticizer(s) is selected such that the refractive index of theplasticizer is at least about 1.460, or greater than about 1.470, orgreater than about 1.480, or greater than about 1.490, or greater thanabout 1.500, or greater than 1.510, or greater than about 1.520. In someembodiments, the high refractive index plasticizer(s) is used inconjunction with a conventional plasticizer, and in some embodiments, ifincluded, the conventional plasticizer is triethylene glycoldi-(2-ethylhexanoate) (“3GEH”). In some embodiments, the refractiveindex of the plasticizer mixture is at least greater than 1.460.

Plasticizers work by embedding themselves between chains of polymers,spacing them apart (increasing the “free volume”) and thus significantlylowering the glass transition temperature (T_(g)) of the polymer resin(typically by 0.5 to 4° C./phr), making the material softer. In thisregard, the amount of plasticizer in the interlayer can be adjusted toaffect the glass transition temperature (T_(g)). The glass transitiontemperature (T_(g)) is the temperature that marks the transition fromthe glassy state of the polymer to the rubbery state. In general, higheramounts of plasticizer loading will result in lower T_(g). Conventionalinterlayers generally have a T_(g) in the range of about 0° C. foracoustic (noise reducing) interlayer to about 45° C. for hurricane andaircraft interlayer applications. A particularly preferred T_(g) forcertain embodiments is in the range of about 28° C. to about 35° C. forthe stiffer layer(s) and about −2° C. to about 5° C. for the softerlayer(s).

An interlayer's glass transition temperature (T_(g)) is also correlatedwith the stiffness of the interlayer, and in general, the higher theglass transition temperature, the stiffer the interlayer. Generally, aninterlayer with a glass transition temperature of 30° C. or higherincreases windshield strength and torsional rigidity. A soft interlayer(generally characterized by an interlayer with a glass transitiontemperature of lower than 30° C.), on the other hand, contributes to thesound dampening effect (i.e., the acoustic characteristics). Theinterlayers of the present disclosure may have glass transitiontemperatures of about 30° C. or greater, or about 35° C. or greater forthe stiffer layer(s), and about 10° C. or less, or about 4° C. or less,or about −5° C. or less, or about −10° C. or less for the soft layer(s).In some embodiments, the multilayered interlayers of the presentdisclosure combine these two advantageous properties (i.e., strength andacoustic) by utilizing harder or stiffer skin layers laminated with asofter core layer (e.g., stiff//soft//stiff) and softer skin layerslaminated with a stiffer core layer (e.g., soft//stiff//soft), whilealso matching the refractive indices of the layers to reduce and/orminimize or eliminate mottle. In various embodiments, the multilayeredinterlayers generally comprise stiffer layer(s) with a glass transitiontemperature of about 25° C. to about 40° C., about 20° C. to about 35°C., about 25° C. to 35° C., about 25° C. or greater, about 30° C. orgreater, and about 35° C. or greater, and softer layer(s) of about 10°C. or less, or about 4° C. or less, or about −5° C. or less, or about−10° C. or less. For example, the following are some typicalmultilayered configurations:

-   -   (T_(g)>25° C.)//(T_(g)<10° C.)//(T_(g)>25° C.) or        (stiff//soft//stiff);    -   (25° C.<T_(g)<40° C.)//(T_(g)<10° C.)//(25° C.<T_(g)<40° C.) or        (stiff//soft//stiff);    -   (T_(g)<35° C.)//(T_(g)>35° C.)//(T_(g)<35° C.) or        (soft//stiff//soft); and    -   (20° C.<T_(g)<35° C.)//(T_(g)>35° C.)//(20° C.<T_(g)<35° C.) or        (soft//stiff//soft).        These configurations are merely exemplary and are in no way        meant to be limiting to the types of multilayered configurations        contemplated by this disclosure.

Additionally, it is contemplated that polymer interlayer sheets asdescribed herein may be produced by any suitable process known to one ofordinary skill in the art of producing polymer interlayer sheets thatare capable of being used in a multiple layer panel (such as a glasslaminate or a photovoltaic module or solar panel). For example, it iscontemplated that the polymer interlayer sheets may be formed throughsolution casting, compression molding, injection molding, meltextrusion, melt blowing or any other procedures for the production andmanufacturing of a polymer interlayer sheet known to those of ordinaryskill in the art. Further, in embodiments where multiple polymerinterlayers are utilized, it is contemplated that these multiple polymerinterlayers may be formed through co-extrusion, blown film, dip coating,solution coating, blade, paddle, air-knife, printing, powder coating,spray coating or other processes known to those of ordinary skill in theart. While all methods for the production of polymer interlayer sheetsknown to one of ordinary skill in the art are contemplated as possiblemethods for producing the polymer interlayer sheets described herein,this application will focus on polymer interlayer sheets producedthrough the extrusion and co-extrusion processes. The final multiplelayer glass panel laminate and photovoltaic module of the presentinvention are formed using processes known in the art.

In its most basic sense, extrusion is a process used to create objectsof a fixed cross-sectional profile. This is accomplished by pushing ordrawing a material through a die of the desired cross-section for theend product.

Generally, in the extrusion process, thermoplastic resin andplasticizers, including any of those resins and plasticizers describedabove, are pre-mixed and fed into an extruder device. Additives such asACAs, colorants and UV inhibitors (in liquid, powder, or pellet form)are often used and can be mixed into the thermoplastic resin orplasticizer(s) prior to arriving in the extruder device. These additivesare incorporated into the thermoplastic polymer resin, and by extensionthe resultant polymer interlayer sheet, to enhance certain properties ofthe polymer interlayer sheet and its performance in the final multiplelayer glass panel product (or photovoltaic module).

In the extruder device, the particles of the thermoplastic raw materialand plasticizers, and any other additives described above, are furthermixed and melted, resulting in a melt that is generally uniform intemperature and composition. Once the melt reaches the end of theextruder device, the melt is propelled into the extruder die. Theextruder die is the component of the thermoplastic extrusion processwhich gives the final polymer interlayer sheet product its profile.Generally, the die is designed such that the melt evenly flows from acylindrical profile coming out of the die and into the product's endprofile shape. A plurality of shapes can be imparted to the end polymerinterlayer sheet by the die so long as a continuous profile is present.

Notably, for the purposes of this application, the polymer interlayer atthe state after the extrusion die forms the melt into a continuousprofile will be referred to as a “polymer melt sheet.” At this stage inthe process, the extrusion die has imparted a particular profile shapeto the thermoplastic resin, thus creating the polymer melt sheet. Thepolymer melt sheet is highly viscous throughout and in a generallymolten state. In the polymer melt sheet, the melt has not yet beencooled to a temperature at which the sheet generally completely “sets.”Thus, after the polymer melt sheet leaves the extrusion die, generallythe next step in presently employed thermoplastic extrusion processes isto cool the polymer melt sheet with a cooling device. Cooling devicesutilized in the previously employed processes include, but are notlimited to, spray jets, fans, cooling baths, and cooling rollers. Thecooling step functions to set the polymer melt sheet into a polymerinterlayer sheet of a generally uniform non-molten cooled temperature.In contrast to the polymer melt sheet, this polymer interlayer sheet isnot in a molten state and is not highly viscous. Rather, it is the setfinal-form cooled polymer interlayer sheet product. For the purposes ofthis application, this set and cooled polymer interlayer will bereferred to as the “polymer interlayer sheet.”

In some embodiments of the extrusion process, a co-extrusion process maybe utilized. Co-extrusion is a process by which multiple layers ofpolymer material are extruded simultaneously. Generally, this type ofextrusion utilizes two or more extruders to melt and deliver a steadyvolume throughput of multiple different thermoplastic melts of differentviscosities or other properties through a co-extrusion die into thedesired final form. The thickness of the multiple polymer layers leavingthe extrusion die in the co-extrusion process can generally becontrolled by adjustment of the relative speeds of the melt through theextrusion die and by the sizes of the individual extruders processingeach molten thermoplastic resin material.

Generally, the thickness, or gauge, of the polymer interlayer sheet willbe in a range from about 15 mils to 100 mils (about 0.38 mm to about2.54 mm), about 15 mils to 60 mils (about 0.38 mm to about 1.52 mm),about 20 mils to about 50 mils (about 0.51 to 1.27 mm), and about 15mils to about 35 mils (about 0.38 to about 0.89 mm). In variousembodiments, each of the layers, such as the skin and core layers, ofthe multilayer interlayer may have a thickness of about 1 mil to 99 mils(about 0.025 to 2.51 mm), about 1 mil to 59 mils (about 0.025 to 1.50mm), 1 mil to about 29 mils (about 0.025 to 0.74 mm), or about 2 mils toabout 28 mils (about 0.05 to 0.71 mm).

As noted above, the interlayers of the present disclosure may be used asa single-layer sheet or a multilayered sheet. In various embodiments,the interlayers of the present disclosure (either as a single-layersheet or as a multilayered sheet) can be incorporated into a multiplelayer panel.

As used herein, a multiple layer panel can comprise a single substrate,such as glass, acrylic, or polycarbonate with a polymer interlayer sheetdisposed thereon, and most commonly, with a polymer film furtherdisposed over the polymer interlayer. The combination of polymerinterlayer sheet and polymer film is commonly referred to in the art asa bilayer. A typical multiple layer panel with a bilayer construct is:(glass) II (polymer interlayer sheet) II (polymer film), where thepolymer interlayer sheet can comprise multiple interlayers, as notedabove. The polymer film supplies a smooth, thin, rigid substrate thataffords better optical character than that usually obtained with apolymer interlayer sheet alone and functions as a performance enhancinglayer. Polymer films differ from polymer interlayer sheets, as usedherein, in that polymer films do not themselves provide the necessarypenetration resistance and glass retention properties, but ratherprovide performance improvements, such as infrared absorptioncharacteristics. Poly(ethylene terephthalate) (“PET”) is the mostcommonly used polymer film. Generally, as used herein, a polymer film isthinner than a polymer sheet, such as from about 0.001 to 0.2 mm thick.

Further, the multiple layer panel can be what is commonly known in theart as a solar panel, with the panel further comprising a photovoltaiccell, as that term is understood by one of ordinary skill in the art,encapsulated by the polymer interlayer(s). In such instances, theinterlayer is often laminated over the photovoltaic cell, with aconstruct such as: (glass)//(polymer interlayer)//(photovoltaiccell)//(polymer interlayer)//(glass or polymer film).

The interlayers of the present disclosure will most commonly be utilizedin multiple layer panels comprising two substrates, preferably a pair ofglass sheets (or other rigid materials, such as polycarbonate oracrylic, known in the art), with the interlayers disposed between thetwo substrates. An example of such a construct would be:(glass)//(polymer interlayer sheet)//(glass), where the polymerinterlayer sheet can comprise multilayered interlayers, as noted above,and wherein the layers of the multilayer interlayer comprise refractiveindex matching plasticizers or one or more high refractive indexplasticizer or combination of plasticizers wherein the refractive indexof the mixture or combination is within the desired range. Stateddifferently, the Delta RI between the layers is minimized (less than0.010), or the Delta RI between the resin and plasticizer is minimized(less than 0.100 or less than 0.075), or the plasticizer is a highrefractive index plasticizer (at least about 1.460), such that mottle inthe multiple layer panel is reduced, and the clarity of the multiplelayer panel is excellent (that is, having minimal haze). These examplesof multiple layer panels are in no way meant to be limiting, as one ofordinary skill in the art would readily recognize that numerousconstructs other than those described above could be made with theinterlayers of the present disclosure.

The typical glass lamination process comprises the following steps: (1)assembly of the two substrates (e.g., glass) and interlayer; (2) heatingthe assembly via an IR radiant or convective means for a short period;(3) passing the assembly into a pressure nip roll for the firstdesiring; (4) heating the assembly a second time to about 60° C. toabout 120° C. to give the assembly enough temporary adhesion to seal theedge of the interlayer; (5) passing the assembly into a second pressurenip roll to further seal the edge of the interlayer and allow furtherhandling; and (6) autoclaving the assembly at temperatures between 135°C. and 150° C. and pressures between 150 psig and 200 psig for about 30to 90 minutes. The actual steps, as well as the times and temperatures,may vary as necessary, as known by one skilled in the art.

Other means for use in de-airing of the interlayer-glass interfaces(steps 2-5) known in the art and that are commercially practiced includevacuum bag and vacuum ring processes in which a vacuum is utilized toremove the air.

Mottle is one measure of optical quality of a laminate. It is seen astexture or graininess and is considered a visual defect if the level ofmottle is too high or too severe (and thus objectionable). As previouslydiscussed, mottle is assessed and categorized by a side-to-sidequalitative comparison of the shadowgraph projections for a testlaminate with a set of standard laminate shadowgraphs representing aseries or scale of mottle values ranging from 1 to 4, with 1representing a standard of low mottle (i.e., a low number ofdisruptions) and 4 representing a standard of high mottle (i.e., a highnumber of disruptions). High mottle is generally considered opticallyobjectionable, particularly in glass panels such as windshields.Optionally, a laminate having a single layer interlayer with zero mottle(or no mottle) is used to facilitate the evaluation of mottle in thetest laminate with a mottle rating lower than the scale of the standardset, such as lower than a rating of 1. The test laminate that shows ashadowgraph projection similar to that of a “zero” mottle laminate isassessed to have a mottle rating of zero (0).

Another parameter used to describe the polymer interlayers disclosedherein is the clarity, which is determined by measuring the haze valueor percent. Light that is scattered upon passing through a film or sheetof a material can produce a hazy or smoky field when objects are viewedthrough the material. Thus, the haze value is a quantification of thescattered light by a sample in contrast to the incident light. The testfor percent haze is performed with a hazemeter, such as Model D25available from Hunter Associates (Reston, Va.), and in accordance withASTM D1003-61 (Re-approved 1977)-Procedure A using Illuminant C, at anobserver angle of 2 degrees. The interlayers of the present disclosurehave a percent haze of less than about 5%, less than about 4%, less thanabout 3%, less than about 2%, less than about 1%, or less than about0.5%.

The glass transition temperature also is used to describe the polymerinterlayers of the present disclosure. The glass transition temperature(T_(g)) was determined by dynamical mechanical thermal analysis (DMTA).The DMTA measures the storage (elastic) modulus (G′) in Pascals, loss(viscous) modulus (G″) in Pascals, loss (damping) factor (LF ortan(delta)) of the specimen as a function of temperature at a givenfrequency, and temperature sweep rate. A frequency of 1 Hz andtemperature sweep rate of 3° C./min were used herein. The T_(g) is thendetermined by the position of the loss factor peak on the temperaturescale in ° C.

Pummel adhesion is another parameter used to describe the polymerinterlayers disclosed herein. The Pummel Adhesion Test is widely usedthroughout the world and has been a standard Solutia Inc., a subsidiaryof Eastman Chemical Company, procedure for over 30 years. It measuresthe adhesion level of glass to the interlayer in a laminateconstruction. The interlayer to glass adhesion has a large effect on theimpact resistance and long term stability of glass-interlayerstructures. In this test, the laminates are cooled to 0° F. (about −18°C.) and manually pummeled with a 1 lb. (about 0.45 kg.) hammer on asteel plate at a 45 degree angle. The samples are then allowed to cometo room temperature and all broken glass unadhered to the interlayer isthen removed. The amount of glass left adhered to the interlayer isvisually compared with a set of standards. The standards correspond to ascale in which varying degrees of glass remained adhered to theinterlayer. For example, at a pummel standard of zero, essentially noglass is left adhered to the interlayer. On the other hand, at a pummelstandard of ten, essentially 100% of the glass remains adhered to theinterlayer. Pummel values are grouped and averaged for like specimens.Reported values state the average pummel value for the group and themaximum range of the pummel adhesion rating for individual surfaces. Theinterlayers of the present disclosure have a pummel adhesion rating ofat least 2, greater than 2, greater than 4, greater than 6, and greaterthan 8.

The refractive index (RI) of the interlayers was measured in accordancewith ASTM D542. The reported RI values are obtained at a wavelength of589 nm and at 25° C.

The invention also includes the following Embodiments 1 to 36, set forthbelow.

Embodiment 1 is a polymer interlayer comprising: poly(vinyl butyral)resin; and at least one high refractive index plasticizer having arefractive index of at least about 1.460; wherein the interlayercomprises about 5 to about 120 parts of the high refractive indexplasticizer mixture per 100 parts poly(vinyl butyral) resin.

Embodiment 2 is a polymer interlayer comprising: poly(vinyl butyral)resin; and at least one high refractive index plasticizer having arefractive index of at least about 1.460; wherein the interlayercomprises about 5 to about 120 parts of the high refractive indexplasticizer mixture per 100 parts poly(vinyl butyral) resin, and whereinthe refractive index of the polymer interlayer is at least 1.480.

Embodiment 3 is a multiple layer polymer interlayer comprising:poly(vinyl butyral) resin; and at least one high refractive indexplasticizer having a refractive index of at least about 1.460; whereinthe multiple layer polymer interlayer has at least one soft layer and atleast one stiff layer, and wherein the difference between the refractiveindex of the soft layer and the stiff layer (Delta RI) is less thanabout 0.010.

Embodiment 4 is a multiple layer polymer interlayer comprising:poly(vinyl butyral) resin; and at least one high refractive indexplasticizer having a refractive index of at least about 1.460; whereinthe multiple layer polymer interlayer has at least one soft layer and atleast two stiff layers wherein the soft layer is disposed between thestiff layers, and wherein the difference between the refractive index ofthe soft layer and the stiff layers is less than about 0.010.

Embodiment 5 is a multiple layer polymer interlayer comprising: a firstlayer comprising poly(vinyl butyral) resin and a first plasticizer; asecond layer comprising poly(vinyl butyral) resin and a secondplasticizer; and a third layer comprising poly(vinyl butyral) resin anda third plasticizer disposed between the first layer and the secondlayer; and wherein at least one of the first, second and thirdplasticizers is a high refractive index plasticizer having a refractiveindex of at least about 1.460; wherein at least one layer is a softlayer and at least one layer is a stiff layer, and wherein thedifference between the refractive index of the soft layer and the stifflayer (Delta RI) is less than about 0.010.

Embodiment 6 is a multiple layer polymer interlayer comprising: a firststiff layer comprising poly(vinyl butyral) resin and a firstplasticizer, wherein the first plasticizer is present in an amount offrom 5 phr to 60 phr; a second stiff layer comprising poly(vinylbutyral) resin and a second plasticizer, wherein the second plasticizeris present in an amount of from 5 phr to 60 phr; and a first soft layercomprising poly(vinyl butyral) resin and a third plasticizer, whereinthe third plasticizer is present in an amount of from 10 phr to 120 phr,and wherein the first soft layer is disposed between the first stifflayer and the second stiff layer; wherein at least one of the first,second and third plasticizers is a high refractive index plasticizerhaving a refractive index of at least about 1.460; wherein thedifference between the refractive index of the soft layer and the stifflayers is less than about 0.010.

Embodiment 7 is a polymer interlayer that includes the features of anyof Embodiments 1 to 6, wherein the high refractive index plasticizer hasa refractive index of at least about 1.470.

Embodiment 8 is a polymer interlayer that includes the features of anyof Embodiments 1 to 7, wherein the high refractive index plasticizer hasa refractive index of at least about 1.480.

Embodiment 9 is a polymer interlayer that includes the features of anyof Embodiments 1 to 8, wherein the high refractive index plasticizer hasa refractive index of at least about 1.490.

Embodiment 10 is a polymer interlayer that includes the features of anyof Embodiments 1 to 9, wherein the difference between the refractiveindex of the resin and the refractive index of the high refractive indexplasticizer is less than about 0.075.

Embodiment 11 is a polymer interlayer that includes the features of anyof Embodiments 1 to 10, wherein the difference between the refractiveindex of the resin and the refractive index of the high refractive indexplasticizer is less than about 0.050.

Embodiment 12 is a polymer interlayer that includes any of the featuresof Embodiments 1 to 11, wherein the high refractive index plasticizerhas a refractive index of from about 1.460 to about 1.560.

Embodiment 13 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 3 to 12, wherein the soft layer comprisesa poly(vinyl butyral) resin having a residual hydroxyl content from 8 to21 wt. %, and wherein the stiff layer comprises a poly(vinyl butyral)resin having a residual hydroxyl content from 16 to 35 wt. %, andwherein the residual hydroxyl content between the adjacent soft andstiff layers differs by at least 2 wt. %.

Embodiment 14 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 3 to 13, wherein the soft layer has aplasticizer content of from 10 phr to 120 phr, and wherein the stifflayer has a plasticizer content of from 5 phr to 60 phr.

Embodiment 15 is a polymer interlayer that includes the features of anyof Embodiments 1 to 14, wherein the polymer interlayer comprises atleast two different high refractive plasticizers, wherein each highrefractive index plasticizer has a refractive index of at least 1.460.

Embodiment 16 is a polymer interlayer that includes the features of anyof Embodiments 1 to 14, wherein the polymer interlayer comprises atleast two plasticizers, wherein at least one plasticizer has arefractive index of at least 1.460 and at least one plasticizer has arefractive index of less than about 1.450.

Embodiment 17 is a polymer interlayer that includes the features of anyof Embodiments 1 to 16, wherein the high refractive plasticizer isselected from dipropylene glycol dibenzoate, tripropylene glycoldibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate,2-ethylhexyl benzoate, diethylene glycol benzoate, propylene glycoldibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate, diethyleneglycol di-o-toluate, triethylene glycol di-o-toluate, dipropylene glycoldi-o-toluate, 1,2-octyl dibenzoate, tri-2-ethylhexyl trimellitate,di-2-ethylhexyl terephthalate, bis-phenol A bis(2-ethylhexaonate),ethoxylated nonylphenol, and mixtures thereof.

Embodiment 18 is a polymer interlayer that includes the features ofEmbodiments 1 to 17, wherein the high refractive plasticizer is selectedfrom dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, and2,2,4-trimethyl-1,3-pentanediol dibenzoate.

Embodiment 19 is a polymer interlayer that includes the features of anyof Embodiments 1 to 18, further comprising an additional plasticizer,wherein the additional plasticizer is triethylene glycoldi-(2-ethylhexanoate).

Embodiment 20 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 3 to 19, wherein the multiple layerpolymer interlayer further comprises a second stiff layer, and whereinthe soft layer is disposed between the stiff layers, or a second softlayer and wherein the stiff layer is disposed between the soft layers.

Embodiment 21 is a multiple layer polymer interlayer that includes thefeatures of Embodiment 15, wherein the at least two different highrefractive plasticizers are in the same layer.

Embodiment 22 is a multiple layer polymer interlayer that includes thefeatures of Embodiment 15, wherein the at least two different highrefractive plasticizers are in different layers.

Embodiment 23 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 5 to 22, wherein the first and secondlayers comprise the plasticizer having a refractive index of at least1.460, and wherein the third layer comprises the plasticizer having arefractive index of less than 1.450.

Embodiment 24 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 5 to 22, wherein the third layercomprises the plasticizer having a refractive index of at least 1.460,and wherein the first and second layers comprise the plasticizer havinga refractive index of less than 1.450.

Embodiment 25 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 5 to 24, wherein the first and secondlayers are stiff layers, and wherein the third layer is a soft layer.

Embodiment 26 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 5 to 24, wherein the first and secondlayers are soft layers, and wherein the third layer is a stiff layer.

Embodiment 27 is a polymer interlayer comprising: poly(vinyl butyral)resin; and a plasticizer mixture comprising: at least one plasticizerhaving a refractive index of less than about 1.450; and at least onehigh refractive index plasticizer having a refractive index of at least1.460; wherein the refractive index of the plasticizer mixture is atleast 1.460; and wherein the interlayer comprises about 5 to about 120parts plasticizer mixture per 100 parts poly(vinyl butyral) resin.

Embodiment 28 is a multiple layer polymer interlayer comprising:poly(vinyl butyral) resin; and a plasticizer mixture comprising: atleast one plasticizer selected from the group consisting of: triethyleneglycol di-(2-ethylhexanoate), triethylene glycol di-(2-ethylbutyrate),triethylene glycol diheptanoate, tetraethylene glycol diheptanoate,tetraethylene glycol di-(2-ethylhexanoate), dihexyl adipate, dioctyladipate, hexyl cyclohexyladipate, diisononyl adipate, heptylnonyladipate, di(butoxyethyl) adipate, bis(2-(2-butoxyethoxy)ethyl) adipate,dibutyl sebacate, and dioctyl sebacate; and at least one high refractiveindex plasticizer having a refractive index of at least 1.460; whereinthe refractive index of the plasticizer mixture is at least 1.460;wherein the multiple layer polymer interlayer has at least one softlayer and at least one stiff layer, and wherein the difference betweenthe refractive index (Delta RI) of the soft layer and the stiff layer isless than about 0.010.

Embodiment 29 is a multiple layer polymer interlayer comprising: a firstlayer comprising poly(vinyl butyral) resin and a first plasticizer; asecond layer comprising poly(vinyl butyral) resin and a secondplasticizer; and a third layer comprising poly(vinyl butyral) resin anda third plasticizer disposed between the first layer and the secondlayer; wherein at least one of the first, second and third plasticizersis a mixture comprising: at least one plasticizer having a refractiveindex of less than about 1.450; and at least one high refractive indexplasticizer having a refractive index of at least 1.460; wherein therefractive index of the plasticizer mixture is at least 1.460; whereinat least one of the layers is a soft layer and at least one of thelayers is a stiff layer, and wherein the difference between therefractive index (Delta RI) of the soft layer and the stiff layer isless than about 0.010.

Embodiment 30 is a polymer interlayer that includes the features of anyof Embodiments 27 to 29, wherein the plasticizer mixture has arefractive index of from about 1.460 to about 1.560.

Embodiment 31 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 28 to 30, wherein the soft layercomprises a poly(vinyl butyral) resin having a residual hydroxyl contentfrom 8 to 21 wt. %, and wherein the stiff layer comprises a poly(vinylbutyral) resin having a residual hydroxyl content from 16 to 35 wt. %,and wherein the residual hydroxyl content between the adjacent soft andstiff layers differs by at least 2 wt. %.

Embodiment 32 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 28 to 31, wherein the soft layer has aplasticizer content of from 10 phr to 120 phr, and wherein the stifflayer has a plasticizer content of from 5 phr to 60 phr.

Embodiment 33 is a polymer interlayer that includes the features of anyof Embodiments 27 to 32, wherein the high refractive index plasticizeris selected from dipropylene glycol dibenzoate, tripropylene glycoldibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate,2-ethylhexyl benzoate, diethylene glycol benzoate, propylene glycoldibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate, diethyleneglycol di-o-toluate, triethylene glycol di-o-toluate, dipropylene glycoldi-o-toluate, 1,2-octyl dibenzoate, tri-2-ethylhexyl trimellitate,di-2-ethylhexyl terephthalate, bis-phenol A bis(2-ethylhexaonate),ethoxylated nonylphenol, and mixtures thereof.

Embodiment 34 is a multiple layer polymer interlayer that includes thefeatures of any of Embodiments 28 to 33, wherein the multiple layerpolymer interlayer further comprises a second stiff layer, and whereinthe soft layer is disposed between the stiff layers or a second softlayer and wherein the stiff layer is disposed between the soft layers.

Embodiment 35 is a multiple layer panel comprising any of the polymerinterlayers of Embodiments 1 to 34.

Embodiment 36 is a method of making the polymer interlayer of any ofEmbodiments 1 to 34.

EXAMPLES

The improvements (or reduction) in the level of mottle and haze in amultilayer interlayer when using a high refractive index plasticizer(s)or mix of plasticizers can be most readily appreciated by a comparisonof multilayer (trilayer) interlayers having a plasticizer that is a highrefractive index plasticizer(s) or a combination of a high refractiveindex plasticizer(s) and a conventional plasticizer (designated as“Disclosed Interlayers”) to a multilayer interlayer having only aconventional plasticizer, such as triethylene glycoldi-(2-ethylhexonate) (“3GEH”) (designated as “ConventionalInterlayers”). The Conventional Interlayers are shown as C1 to C7 inTable 1, and the Disclosed Interlayers are shown in Table 2 to Table 6below). These Examples demonstrate the difference in refractive index(Delta RI) between the layers can be minimized and the optical quality(mottle and haze or clarity) improved when a high refractive indexplasticizer(s) is used either alone or in combination with one or moreplasticizers.

The Disclosed and Conventional Interlayers were produced by mixing andmelt-extruding mixtures of 100 parts poly(vinyl butyral) resin andplasticizer, and other common additives. The types and amounts ofplasticizers used are shown in the Tables below. Plasticizers arelabeled as A, B, C, D, E or F, where C is the Conventional Plasticizer,3GEH, and A, B, D, E and F are each high refractive index plasticizersor mixtures of plasticizers as shown below and in the Tables. Thepoly(vinyl butyral) resin used in the stiff (skin) layer had about 18 to19 wt. % residual hydroxyl content and a vinyl acetate residue of 2%,and the poly(vinyl butyral) resin used in the soft (core) layer hadabout 10 to 11 wt. % residual hydroxyl content and a vinyl acetateresidue of 2%. The amounts of plasticizer, the refractive indices, andthe Delta RI results are as shown below in Table 1 to Table 6.

Plasticizers used:

Plasticizer A: Dioctyl Terephthalate (RI—1.487)

Plasticizer B: Mixture of 30% 3GEH and 70% Benzoflex 2088* (wt./wt.)

(RI of the mixture—1.510, Benzoflex 2088 RI—1.539)

Plasticizer C: 3GEH (RI—1.442) (Conventional Plasticizer)

Plasticizer D: Nonylphenol Tetra-ethylene Glycol (RI—1.497)

Plasticizer E: Mixture of 50% 3GEH and 50% Benzoflex 2088* (wt./wt.)

(RI of the mixture—1.491, Benzoflex 2088 RI—1.539)

Plasticizer F: Mixture of 25% 3GEH and 75% Benzoflex 9-88** (wt./wt.)

(RI of the mixture—1.507, Benzoflex 9-88 RI—1.528)

TABLE 1 Conventional Interlayers Plasticizer C: 3GEH (RI - 1.442)(Conventional Plasticizer) Skin Core Plasticizer Plasticizer Sample(phr) Skin RI (phr) Core RI Delta RI C1 40 1.476 40 1.473 0.003 C2 401.476 50 1.471 0.005 C3 40 1.476 60 1.469 0.007 C4 40 1.476 70 1.4670.009 C5 40 1.476 80 1.466 0.010 C6 40 1.476 90 1.465 0.011 C7 40 1.476100 1.464 0.012

TABLE 2 Plasticizer A: Dioctyl Terephthalate (RI - 1.487) Skin CorePlasticizer Plasticizer Sample (phr) Skin RI (phr) Core RI Delta RI A140 1.489 40 1.486 0.003 A2 40 1.489 50 1.486 0.003 A3 40 1.489 60 1.4860.003 A4 40 1.489 70 1.486 0.003 A5 40 1.489 80 1.486 0.003 A6 40 1.48990 1.486 0.003 A7 40 1.489 100 1.486 0.003

TABLE 3 Plasticizer B: Mixture of 30% 3GEH and 70% Benzoflex 2088*(wt./wt.) (RI of the mixture - 1.510, Benzoflex 2088 RI - 1.539) SkinCore Plasticizer Plasticizer Sample (phr) Skin RI (phr) Core RI Delta RIB1 40 1.496 40 1.492 0.004 B2 40 1.496 50 1.493 0.003 B3 40 1.496 601.494 0.002 B4 40 1.496 70 1.495 0.001 B5 40 1.496 80 1.496 0.000 B6 401.496 90 1.497 0.001 B7 40 1.496 100 1.498 0.002 *Benzoflex 2088 isplasticizer that is a mixture of benzoates

TABLE 4 Plasticizer D: Nonylphenol Tetra-ethylene Glycol (RI - 1.497)Skin Core Plasticizer Plasticizer Sample (phr) Skin RI (phr) Core RIDelta RI D1 40 1.492 40 1.488 0.004 D2 40 1.492 50 1.489 0.003 D3 401.492 60 1.490 0.002 D4 40 1.492 70 1.490 0.002 D5 40 1.492 80 1.4900.003 D6 40 1.492 90 1.491 0.001 D7 40 1.492 100 1.491 0.001

TABLE 5 Plasticizer E: Mixture of 50% 3GEH and 50% Benzoflex 2088*(wt./wt.) (RI of the mixture - 1.491, Benzoflex 2088 RI - 1.539) SkinCore Plasticizer Plasticizer Sample (phr) Skin RI (phr) Core RI Delta RIE1 40 1.490 40 1.487 0.003 E2 40 1.490 50 1.487 0.003 E3 40 1.490 601.487 0.003 E4 40 1.490 70 1.487 0.003 E5 40 1.490 80 1.488 0.002 E6 401.490 90 1.488 0.002 E7 40 1.490 100 1.488 0.002 *Benzoflex 2088 isplasticizer that is a mixture of benzoates

TABLE 6 Plasticizer F: Mixture of 25% 3GEH and 75% Benzoflex 9-88**(wt./wt.) (RI of the mixture - 1.507, Benzoflex 9-88 RI - 1.528) SkinCore Plasticizer Plasticizer Sample (phr) Skin RI (phr) Core RI Delta RIF1 40 1.495 40 1.491 0.004 F2 40 1.495 50 1.492 0.003 F3 40 1.495 601.493 0.002 F4 40 1.495 70 1.494 0.001 F5 40 1.495 80 1.495 0.000 F6 401.495 90 1.485 0.000 F7 40 1.495 100 1.496 0.001 **Benzoflex 9-88 is adipropylene glycol dibenzoate plasticizer

Tables 1 to 6 show that for the Conventional Interlayers, which includeconventional plasticizer (such as 3GEH) having a refractive index ofless than about 1.450, as the level of plasticizer in the soft (core)layer is increased from 40 phr to 100 phr, the Delta RI between the soft(core) and the stiff (skin) layers increases significantly from 0.003 at40 phr to 0.012 at 100 phr, as shown in Table 1. This fourfold increasein the Delta RI between the soft (core) and the stiff (skin) layers willtranslate to an increased level of mottle or a higher mottle rating, aswell as higher haze, in the multilayer glazing panel, as furtherdiscussed below.

Where a high refractive index plasticizer or mix of plasticizersincluding at least one high refractive index plasticizer is used, suchthat the refractive index is greater than about 1.460 (and higher thanthe RI of the conventional plasticizer), the Delta RI between the soft(core) and the stiff (skin) layers did not increase significantly as thelevel of plasticizer in the soft (core) layer increased, as shown inTables 2 to 6. With some plasticizers, the Delta RI did not change,while in others, the change was from 0.001 to 0.004. In some cases, theDelta RI stayed essentially the same or was even reduced. As shown inTable 2, when Plasticizer A (RI of 1.487) was used, the Delta RI was thesame regardless (0.003) of the amount of plasticizer in the soft (core)layer. As shown in Table 3, when Plasticizer B (a mixture of aconventional plasticizer and a high refractive index plasticizer,wherein the mixture had an RI of about 1.510) was used, the Delta RIvaried slightly, from 0.004 at 40 phr Plasticizer B in the soft (core)layer, to zero at 80 phr in the soft (core) layer, to 0.002 at 100 phrin the soft (core) layer. Using Plasticizer D (RI of 1.497), as shown inTable 4, had similar results to those in Table 3, where the Delta RIvaried slightly from 0.004 to 0.001 depending on the level ofPlasticizer D in the soft (core) layer. Using a mixture having adifferent ratio of conventional plasticizer to high refractive indexplasticizer (Plasticizer E) produced a more consistent, but still verylow, Delta RI, as shown in Table 5, where the Delta RI was 0.003 atplasticizer levels of 40 to 70 phr in the soft (core) layer, and 0.002at plasticizer levels of 80 to 100 phr in the soft (core) layer.Finally, using a different mixture of plasticizers (Plasticizer F)produced similar variation in Delta RI as that in Table 3. Regardless ofwhich high refractive index plasticizer or mix of plasticizers having atleast one high refractive index plasticizer was used, the Delta RI wasconsistently lower and less variable than when a conventionalplasticizer (Plasticizer C) was used.

The multilayer interlayers listed in Table 7 were produced by mixing andmelt co-extruding the mixtures of 100 parts poly(vinyl butyral) resinwith a plasticizer or plasticizer mix (A, B, C, E or F as previouslydescribed above), and other common additives. The poly(vinyl butyral)resin used in the stiff (skin) layer had about 18 to 19 wt. % residualhydroxyl content and a vinyl acetate residue of 2%, and the poly(vinylbutyral) resin used in the soft (core) layer had about 10 to 11 wt. %residual hydroxyl content and a vinyl acetate residue of 2%. All of themultiple layer interlayers in Table 7 were produced by co-extruding themixtures of resin and plasticizer for the stiff (skin) and soft (core)layer layers to form multilayer interlayer sheets at standardconditions. The surface roughness, Rz, for all the interlayers in Table7 was about 42 to 45 microns. The type and amount of plasticizer usedand the respective refractive indices of the layers are shown in Table7. Additionally, the level of mottle of the multiple layer interlayersheet in a laminated multiple layer glass panel was measured and isshown in Table 7 below. One Conventional and one exemplary DisclosedInterlayer (samples G1 and G5 respectively) were also tested for Hazeand Pummel Adhesion levels, to demonstrate that other performanceproperties and characteristics of the interlayer were not adverselyaffected by the inclusion of a high refractive index plasticizer (or mixof plasticizers comprising at least one high refractive indexplasticizer and having a high refractive index for the mixture).

TABLE 7 Skin Core Plasticizer Skin Plasticizer Core Delta Pummel SamplePlasticizer (phr) RI (phr) RI RI Mottle % Haze Adhesion G1 C 38 1.477 751.467 0.010 >4 0.2 3 G2 E 40 1.490 80 1.488 0.002 0 NT NT G3 B 40 1.49684 1.496 0.000 0 NT NT G4 A 38 1.489 75 1.486 0.003 <1 NT NT G5 F 421.495 84 1.495 0.000 0 0.2 3 NT—Not Tested

Table 7 shows that for the Disclosed Interlayer samples (which includeda high refractive index plasticizer or mixture of plasticizerscomprising at least one high refractive index and having a highrefractive index for the mixture), the difference between the refractiveindices of the skin and core layers for the samples with the highrefractive index plasticizer(s) is lower (that is, less than 0.010, oreven less than 0.004, or 0.003 or less) than the difference between therefractive indices of the stiff (skin) and soft (core) layers of theinterlayers with the Conventional Plasticizer. Additionally, as shown inTable 7, the mottle of the Disclosed Interlayers was less than 1, oreven rated as 0, which is significantly lower than the mottle in theConventional Interlayer, which was greater than 4, thus producing aninterlayer sheet with improved optical quality and very low mottle.

Haze and Pummel Adhesion levels were tested on one ConventionalInterlayer and one Disclosed Interlayer (Samples G1 and G5respectively), and there was no difference between them, showing thatthere is no adverse effect due to the use of a high refractive indexplasticizer.

In conclusion, the interlayers comprising high refractive indexplasticizer(s) as described herein have advantages over interlayersusing conventional plasticizer having a lower refractive index aspreviously utilized in the art. In general, use of a high refractiveindex plasticizer either alone or in combination with a conventionalplasticizer and/or a second high refractive index plasticizer results insignificantly decreased levels of mottle and good clarity (i.e., lowhaze) therefore improved optical quality interlayers. Other advantageswill be readily apparent to those skilled in the art.

While the invention has been disclosed in conjunction with a descriptionof certain embodiments, including those that are currently believed tobe the preferred embodiments, the detailed description is intended to beillustrative and should not be understood to limit the scope of thepresent disclosure. As would be understood by one of ordinary skill inthe art, embodiments other than those described in detail herein areencompassed by the present invention. Modifications and variations ofthe described embodiments may be made without departing from the spiritand scope of the invention.

It will further be understood that any of the ranges, values, orcharacteristics given for any single component of the present disclosurecan be used interchangeably with any ranges, values or characteristicsgiven for any of the other components of the disclosure, wherecompatible, to form an embodiment having defined values for each of thecomponents, as given herein throughout. For example, an interlayer canbe formed comprising poly(vinyl butyral) having a residual hydroxylcontent in any of the ranges given in addition to comprising aplasticizers in any of the ranges given to form many permutations thatare within the scope of the present disclosure, but that would becumbersome to list. Further, ranges provided for a genus or a category,such as phthalates or benzoates, can also be applied to species withinthe genus or members of the category, such as dioctyl terephthalate,unless otherwise noted.

The invention claimed is:
 1. A multiple layer polymer interlayercomprising: a first polymer layer comprising a thermoplastic resin and afirst plasticizer; and a second polymer layer comprising a thermoplasticresin and a second plasticizer; wherein at least one of the firstplasticizer and second plasticizer comprises a high refractive indexplasticizer having a refractive index of at least about 1.460; whereinthe first polymer layer is softer than the second polymer layer, andwherein the interlayer has a refractive index of at least about 1.480.2. The polymer interlayer of claim 1, wherein the first plasticizercomprises at least two different plasticizers, wherein at least oneplasticizer has a refractive index of at least 1.460 and wherein atleast one plasticizer has a refractive index of less than about 1.450.3. The polymer interlayer of claim 1, wherein the high refractive indexplasticizer is selected from dipropylene glycol dibenzoate, tripropyleneglycol dibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate,2-ethylhexyl benzoate, diethylene glycol benzoate, propylene glycoldibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate, diethyleneglycol di-o-toluoate, triethylene glycol di-o-toluoate, dipropyleneglycol di-o-toluoate, 1,2-octyl dibenzoate, tri-2-ethylhexyltrimellitate, di-2-ethylhexyl terephthalate, bis-phenol Abis(2-ethylhexaonate), ethoxylated nonylphenol, and mixtures thereof. 4.The polymer interlayer of claim 1, wherein at least one of the firstpolymer layer and the second polymer layer comprises poly(vinylbutyral).
 5. The polymer interlayer of claim 1, wherein the differencebetween the refractive index of the first polymer layer and the secondpolymer layer is less than about 0.009.
 6. The polymer interlayer ofclaim 1, wherein the difference between the refractive index of thefirst polymer layer and the second polymer layer is less than about0.005.
 7. A multiple layer polymer interlayer comprising: a firstpolymer sheet comprising a thermoplastic polymer and from 5 phr to 60phr of a first plasticizer and having a refractive index; a secondpolymer sheet comprising a thermoplastic polymer and from 10 phr to 120phr of a second plasticizer and having a refractive index; wherein thesecond polymer layer is softer than the first polymer layer, and whereinthe interlayer has a refractive index of at least about 1.480, andwherein at least one of the first plasticizer and second plasticizercomprises a high refractive index plasticizer having a refractive indexof at least about 1.460; wherein the difference between the refractiveindex of the first polymer layer and the second polymer layer is lessthan about 0.009.
 8. The polymer interlayer of claim 7, wherein thefirst plasticizer and the second plasticizer are different.
 9. Thepolymer interlayer of claim 7, wherein the first polymer layer has afirst residual hydroxyl content and the second polymer layer has asecond residual hydroxyl content, and wherein the difference between thefirst residual hydroxyl content and the second residual hydroxyl contentis at least 2 weight percent.
 10. The polymer interlayer of claim 7,wherein at least one of the first polymer layer and the second polymerlayer has a refractive index of at least 1.480.
 11. The polymerinterlayer of claim 7, wherein the first plasticizer comprises at leasttwo different plasticizers, wherein at least one plasticizer has arefractive index of at least 1.460 and wherein at least one plasticizerhas a refractive index of less than about 1.450.
 12. The polymerinterlayer of claim 7, wherein at least one of the first polymer layerand the second polymer layer comprises poly(vinyl butyral).
 13. Thepolymer interlayer of claim 7, wherein the difference between therefractive index of the first polymer layer and the second polymer layeris less than about 0.005.
 14. A multiple layer polymer interlayercomprising: a first polymer layer comprising poly(vinyl butyral) resinand a first plasticizer wherein the first polymer layer has a firstresidual hydroxyl content; a second polymer layer comprising poly(vinylbutyral) resin and a second plasticizer wherein the second polymer layerhas a second residual hydroxyl content; wherein at least one of thefirst plasticizer and second plasticizer comprises a high refractiveindex plasticizer having a refractive index of at least about 1.460; andwherein the first polymer layer is softer than the second polymer layer,wherein the difference between the first residual hydroxyl content andthe second residual hydroxyl content is at least 2 weight percent, andwherein the difference between the refractive index of the first polymerlayer and the second polymer layer is less than about 0.009.
 15. Thepolymer interlayer of claim 14, wherein the first plasticizer comprisesat least two different plasticizers, wherein at least one plasticizerhas a refractive index of at least 1.460 and wherein at least oneplasticizer has a refractive index of less than about 1.450.
 16. Thepolymer interlayer of claim 14, wherein at least one of the firstpolymer layer and the second polymer layer has a refractive index of atleast 1.480.
 17. The polymer interlayer of claim 14, wherein thedifference between the refractive index of the first polymer layer andthe second polymer layer is less than about 0.005.